Method of producing alloyed iron rolls



Fatented May 7, 1946 Q METHOD OF PRODUCING more mom ROLLS Albert PaulGagnebln, Red Bank, and Edmund Merriman Wise, Westiield, N. J.,asslgnors to The International Nickel Company, linc., New York, N. Y., acorporation of Delaware No Drawing. Application May 4, 1942, Serial No.441,726

14' Claims.

The present invention relates to rolls and more particularly to hardalloyed cast iron rolls having a hard body and machinable necks and thelike.

It is well known that the more fully alloyed cast iron rolls of thechilled type possess certain advantages but these rolls suffered from thdisadvantage that when cooled from the cast condition in theconventional manner the necks of the rolls, i. e., the parts of therolls which rest in chucks or hearings, were unmachinable. Thisnecessitated the use of slow expensive operations to shape the rollnecks, usually by grinding. These operations were necessary because thecomposition of the roll is governed by the requirements of the chilledbody where a very hard, mirror-like surface is required. The amounts ofalloying elements in the cast iron are usually controlled at asufficiently high level to produce a hard martensitic matrix structurein the roll body. As a result, the necks also developed a martensiticmatrix structure and were also hard and unmachinable. Attempts have beenmade to soften the martensitized roll necks by heating them but thistreatment often results in cracking or weakening the material near thejunction between the neck and the body of the roll and is also veryslow, about 4 to 6 days being required for accomplishing this treatment.Due to the inherently unsatisfactory nature of this process, the necksare frequently left hard and are ground to dimensions, which,while slowand costly, about $600 per pair of rolls or more than 15% of the totalcost, avoids the hazards of the reheating process. To avoid this slowand costly grinding operation it has been proposed to use. a processwhich consists'in the mold with the regular roll alloy, waiting Ior'fashort time to permit the. formation of a shell in the chilled body, thendraining out the molten portion of the roll alloy and refilling the moldwith a less alloyed composition or plain iron which would provide a softneck which could be machined. While this method has been tried incertain types of rolls, it had several disadvantages. The most seriousof these was that the chilled body shell frequently cracked and, besidesthe obvious mechanical diiliculties involved in this production method,the roll suffered some loss in scrap value because its averagecomposition was unknown. This method required very exact timing, perfectcontrol of pouring tern; peratures, extreme care in pouring and otheraccurately controlled conditions and, as far as known, attempts to useit have been abandoned in the United States.

a An outgrowth of the above process is the scheme of pouring in enoughmetal to fill the mould for the lower neck and the roll bodyand then tofollow this with a small amount of bottom poured plain cast iron whichdilutes the metal in the lower neck and renders it less hard and more orless simultaneously pouring in a small amount of plain cast iron intothe top of the mould to form the neck at the upper end of the rollcasting. 'This too requires great skill and very accurate control of thevolumes of hot metal, but the worn rolls. and the compositions of thenecks are not identical and their properties are somewhat variabledepending, as they do, on the amount of mixing that has occurred, bothfeatures being objectionable. Attempts were also made to softenmartensitic roll necks by reheating them while the roll body was keptcool enough to avoid softening it. However, severe thermal stresses wereset up in the brittle martensite which initially constitutes both theneck and the body of the roll with the result that cracks oftendeveloped in a new roll which would cause the necks to break of! whenlifted with a crane or still worse. the high stresses or minute cracks,in the weak region near the junction of the body of the roll and theneck, would cause failure during use which would result in the shut downof a whole continuous strip mill.

Great effort has been made to mitigate these difi'iculties and whilconsiderable progress has been effected this treatment is inherentlyprecarious due to the brittleness of the martensite and the largethermal stresses which are set up by the diilerential heating of a massof meta] weighing from l0000..to 20000 lbs. It is also slow, some 4 to 6days being required to perform it.

Although'many attempts have been made to remedy the foregoingshortcomings, none, as far as we are aware was entirel successful whencarried into practice on an industrial scale. We have discovered that aroll can be obtained having the same composition in the neck as in thebody and having a machinable neck and a hard face or chill on the bodyby a special treatment which'involves arresting the cooling of the necksafter casting for a period of time in a range of elevated temperatures.While diamonds and perhaps some of the special carbide tools may cut themartensitic irons, we consider that machinability with reference to rollnecks means that the neck can be cut in a practical manner with toolsmade of good high speed steel.

It is an object of the present invention to provide a method ofproducing an alloyed cast iron roll having a body with a hardmartensitic face, and: integral with it, one or more necks having thesame composition as the body, and comprising a machinable substantiallynonmartensitic structure, whereby the roll neck may be machined.

It is another object of the present invention to provide a method oftreating cast.iron rolls which would have unmachinable necks afterconventional cooling from casting solidification temperatures to rendersaid necks machinable and at the same time to retain a hard face orchill on the body of said rolls.

Other objects and advantages of the present invention will becomeapparent to those skilled in the art from the following description.

Broadly stated, the invention comprises casting an alloyed martensiticcast iron roll-having a body and necks; cooling the metal in said 'castroll from solidification temperatures; arresting the cooling of themetal in said necks within the range of about 500 F. to slightly belowthe temperature at which austenite is stable. The latter temperature, asis well known in the art, varies with the composition of the austenitebut normally will not exceed 1400 F. even in compositions containingappreciable chromium and like elements. The rate of decomposition ofaustenite is very slow just below the temperature at which austenite isstable but becomes more rapid as the temperature is lowered, reaches amaximum rate and again becomes slow as temperatures of the order of 500F. are approached. We therefore arrest the cooling at a temperature atwhich austenite transforms at a reasonable rate; i. e., a temperaturenormally below 1400 F. and generally below 1300 F. and preferably 900 F.to 1100 F., while continuing the cooling of the metal in the body ofsaid roll. The invention further comprises maintaining said necks withinsaid temperature ran e for a period of time suflicient to transform thenecks to a machinable In actual practice, the roll is ordinarily castvertically, in accordance with preferred commercial procedure, in a moldwith chillers around the body and sand around the necks. After the roll,(plus its necks) has been poured it may be allowed to cool in the moldor may "be stripped from the mold, e. g., at about black or dull redheat, and be placed in an annealing oven, e. g., at about 1000 F., tocool or may be covered with a heat insulating medium to retard thecooling depending upon the type of hard iron employed, stripping andoven cooling being preferred with the high chromium type of irons soldunder the trade-mark Ni-Hard" to avoid cracking, while mold cooling issatisfactory for the low chromium type of iron sold under the trade markNi- Hard and allied roll compositions. Stripping from the vmold followedby'air cooling is employed in a few instances with rolls of low alloycontent. The invention may be applied to rolls stripped from the moldsand cooled in air or to rolls cooled in the molds, as well as in ovens,furnaces, pitS, etc. In accordance with the present invention the entireroll is not then slowly cooled to atmospheric temperatures but, on thecontrary, the necks of the roll are maintained at temperatures withinthe range set forth hereinbefore for transforming the necks to amachinable structure, e, g., at a temperature within the range of about850 F. to about 1200 F., say at about 1000 F., for the specified periodof time, e. g., about 10 to 50 hours, whilst the body of the roll isslowly cooling. The necks of the roll are maintained at the desiredtemperature or temperatures within the specified range by the localapplication of heat to the roll necks. Where rolls are to be cooled inthe mold, which ourrently is the most generally employed method,

' s'istance heating is ordinarily most convenient,

structure, say for a period of time generally exceeding one hour, (whichwould only be useful for a rapidly transforming low alloy composition)but generally about 10 to about 200 hours, preferably about 10 to abouthours, while continuing the cooling of the metal in said roll body; andthereafter cooling the thus treated metal of said necks and cooling themetal of said body to a temperature low enough for the body to transformto martensite, whereby an alloyed cast iron roll is obtained having ahard martensitic body face and integral therewith machinable necks ofthe same composition as said roll body. By martensite we mean astructure resulting from the decomposition of austenite at or belowabout 500 F. and generally above about 200 F. It is a feature of thepresent invention that the cooling of the necks is interrupted duringthe original cooling from casting without first cooling to roomtemperatures, which would result in the production of martensite, andthen reheating, and that the isothermal treatment of the roll necksoccurs while the roll body-is still above atmospheric temperatures,preferably whilethe roll body is still .in the austenitic condition andbefore the body or body face transforms to marten site, which usuallytakes place in the range of about 500 F. to about 200 F.

induction heating can be employed if desired. Hollow coils may also beemployed as described below.

Where rolls are stripped from the mold while hot, a satisfactory methodof heating the necks comprises placing heating coils about them, e. g.,placing a tube or sleeve furnace about each neck to be treated, andplacing the entire assembly into an annealing oven, pit, or otherapparatus adaptable for the conventional slow cooling of rolls. Gasflames can be used for heating the necks but are not preferred. Anysource of heat may be used, e. g., resistance furnace, inductionheating, etc., and hollow coils may be employed so that an appropriatecooling medium can be blown through them to accelerate the attainment ofthe desired temperature in the neck. Heat is then applied to the necks,e. g., through the heating coils,

to maintain the necks at substantially constant temperatures, 1. e., attemperatures within the range specified herein, while the roll body iscooling slowly in the conventional manner. In commercial practice rollscooling in chillers in the mold cool rapidly at high temperatures andmore slowly as the temperature falls. and the cooling rate will decreasesomewhat with an increase in the diameter of the roll. As a typicalexample it may be'noted that a 26" roll will cool at the rate of about40 F./hour at 1000 F. and about 20 F./hour at 700 F; In rolls that arestripped and placed in a furnace the cooling rate can be reduced as maybe required to avoid cracking. It is preferred to so control the slowcooling of the roll body that the isothermal transformation of the rollnecks is substantially completed while the body of the roll is stillaustenitlc. The necks are We are of the opinion that the lowest residualstress-Will result if the temperature of the roll neck is slightly aboverather than below that Of the body of the roll at the time the lattermarten-' sitizes as the volume of the roll increases when itmartensitizes.

The hardness of roll necks produced by slow cooling in the conventionalmanner will depend on the proportion of carbide and graphite even thoughthe matrix is martensitic. The difference in hardness of the neck afterhaving been given the isothermal treatment as compared to the hardnessof the neck obtained on continuous slow cooling will be roughly thesameregardless of the degree of mottle (proportion of graphite tocarbide) However, the length of time required to complete the isothermaltransformation of the necks will vary inversely with the degree ofmottle.

After the prescribed isothermal treatment, the roll necks are thenslowly cooled to temperatures approaching atmospheric temperatures Whilethe slow cooling of the roll body is continued. After the body of theroll has cooled low enough to permit martensitization to occur, the rollis pref- 'erably given the usual stress relieving treatment. e. g.,heating at-about 400 F. to 600 F. followed by slow cooling. Alloyed castiron rolls produced in accordance with the foregoing are characterizedby a hard martensitic face or chill on the roll body and by machina bleroll necks integral therewith and of the same composition as the rollbody.

As an illustrative example, we may consider the isothermal treatment ofthe metal of a roll neck having the composition suitable for definitechill rolls, and sold under the trade-mark of Ni- Hard. When theisothermal treatment of such a roll neck is conducted at temperatures ofbout 1000 F. to about 1200 F. for about 10 to about '50 hours thehardness of the roll neck is lowered as much as from about 175 to 230points Brinell below the hardness which would be secured by continuousslow cooling from solidification temperatures. While somewhat softerstructures may be obtained in rolls made of the composition sold underthe trade-mark of "Ni-Hard by treatment at about 1100 F. and about 1200"F.,.the time required for transformation of the metal in the neck isgreater than at approximately 1000 F. and it is preferred to use thelatter approximate temperature in interrupting the cooling of the roll.neck for the isothermal transformation thereof. It has been found: thatthe structure of the metal has a more important effect uponmachinability than the hardness. Thus, irons having a matrix structure.madeup of peariitic and closely related transformation products withhardnesses up, to about 510 Brinell could be machined while irons havinga heavily mottled, martensitic structure with about 375 Brinell hardnesscould not be machined. The aim in isothermally treating the roll necksis primarily to obtain a structure. on the part of the roll neck to bemachined, which is machinable rather than merely to obtain minimumhardness which is not always desirable as it may reduce the strengthunduly.

The matrix structures developed in the necks will depend upon thetemperature and time used for the isothermal treatment as well as thecomposition of the roll and neck, as those skilled in the art willreadily understand. High temperatures will result in coarse pearlite,lower temv peratures in fine pearlite and still lower temperatures inacicular intermediate transformation products including some types whichmay be called Bainite. All of these structures can be machined althoughwith increasing difficulty in the order named. The desired matrixstructure of the neck is defined to include any machinable austenitedecomposition product such as coarse or fine pearlite and otherintermediate transformation products including all which are developedupon cooling or holding at suitable intermediate temperatures aboveabout 500 F. We desire to exclude martensite and tempered martensitewhich may be called sorbite. the transformations described herein areincomplete and while a large amount of pearlite is desirable in thematrix, satisfactory machinability of the necks can be securedwith about50% pearlite or allied intermediate austenite decomposi-' tion product,the remainder may be martensite or some related structure. The usualcarbides and graphite will be embedded in this matrix. It "is to beobserved that the matrix microstructure obtained by the presentinvention is different from that .obtained by reheatingmartensitizedroll necks to the temperature which would be used for the, isothermaltransformation or other temperature at which tempering could-beaccomplished. The face or chill of the body of rolls produced inaccordance with the present invention is generally martensitic, i. e.,the microstructure has a martensitic matrix, plus the usual carbidesembedded in the matrix; Grain rolls will also contain some graphite inthe face of the roll. The martensitic matrix of the hard face or chillmay, and usually does, extend deep into the roll body. In depth the'microstructure is' usually made up of graphite in a martensitic matrix.In addition to graphite, carbides may also be present in some instances.While the matrix usually willbe largely martensitic; other products mayalso be present. The change in 'microstructure from neck to roll body isgradual and may extend over a few inches, usually into the body of theroll. The transition zone usually contains less and finer pearlite as itblends into the structure of the roll proper, thus assuring greaterstrength at the. junction between the roll and the neck.

The isotherlrialtreatment contemplated by the present invention may beaccomplished in various manners. Thus, for rolls that are :to be cooledinthe mold, a helix of electric resistance wire may be embedded. in thesand aroundthe neck when ramming the mold. When the neck of the castroll has cooledto about l000 F., as

determined by a thermo-coupleembedded in the sand around the neck, thehelix may be connected toa sultable'source of electrical power and thetemperature of the neck controlled at say about 1000" F. for the timerequired to develop the desired machinable structure. An alternativemethod comprises placing tube furnaces over the necks after the roll isstripped from its mold to maintain the desired constant temperature inthe necks until the isothermal transformation has occurred therein. Itis usually necessary, however,

Generally to protect ,the body from too fast a cooling rate which may bedone in various ways, for example, by placing the roll and its neckfurnaces in a preheated furnace so as to allow the body of the roll tocool very gradually, while the tube furnace is holding the temperatureof the neck at about 1000 F. or any other desired transformationtemperature. Also, the cooling rate of the body can be slowed up bycovering the body of the roll with some insulating material, such asinfusorial earth or fine sand.

It shouldbe noted that the present invention differs radically fromcooling the body and neck of theroll to room temperature, which resultsin. martensitizing both portions, and then heating the neck to soften itfor machining. The

latter process sets up very high stresses between the hot roll neck andthe cold martensitic roll body and produces a weak transition zone whichfrequently cracks or breaks when such rolls are put into service. In thepresent invention the pearlite transformation of the rollneck ispreferably accomplished while the roll body is in the plastic austeniticcondition when it is better adapted to withstand the stresses set up ator near the junction of the body and neck than is a brittle martensiticroll body. However, with small rolls, which can be cooled safely atsomewhat higher rates than large rolls, and with rolls which contain asub-normal amount ofalloying elements and as a result must be cooled atvarious high rates to develop adequate hardness, the isothermaltransformation of the roll neck may not be completed prior to themartensitization of the body of the roll, a result which,

while not so desirable as that outlined above, is

permissible under the circumstances and yields a reasonably goodproduct; in any event it is superior to the old process where the rollbody and the necks are cooled to a sufficiently low temperature totransform to mazrtensite and then the necks are reheated to soften them.

Another, although less preferred procedure, in accordance with the.present invention, involves accelerating the cooling of the necks tothedesired temperature for the isothermal transformation, for example,about 1000" F., by blowing air thereon, for example through asurrounding coil which later could be employed to supply heat, and thenholding the neck at about this temperature while the roll body cools atany desired rate. In this procedure, the neck would be held for amaximum percentage of the total cooling time in the temperature rangewhere the isothermal transformation occurs at the highest rate. Afterthe transformation of the necks has proceeded sumciently to yield thedesired machinable structure, the necks may be cooled to approximatelythe temperature of the roll, preferably by passing air roll are cooledtogether. This procedure, while slightly more invol may be expected togive the minimum stres at the junction of the roll body and the neck.Under some circumstances, the accelerated cooling of the neck in theearly part of the above cycle may lead to the retention of slightly morecarbon in solid solution which may render the isothermal transformationmore sluggish but the various other advantages of the modification oftheprocess are frequently more important than this effect. Under somecircumstances the accelerated cooling will only be applied after' theisothermal transformation with the object of bringing the neck and rollto apascenao proximate temperature equality at the time ofmartensitization of the roll body.

While the invention has been described in con- Junction with roll necks,it is to be clearly understood that the present invention is equallyapplicable not only to roll necks but to extensions of roll necks suchas wobblers and to other parts integrally cast with the roll body andsubsequently machined and we use the term "necks in its broad sense toinclude such extensions of roll necks and similar constructions whichare to be machined. Similarly, while there are usually two necks, withor without extensions, etc., on each roll which must be machined ordressed it will be apparent that the invention is applicable also to thetreatment of one roll neck where it is desired to machine only one neckand where reference is made to roll "necks it is not intended to excludetreatment of a single roll neck to render it machinable. shaped byturning, there are numerous other machlning jobs on necks depending onthe type of .roll, such as drilling operations, keying, etc.,

is likely to be hotter than the cope neck if all the metal required tofill the mold is poured through thebottom gate or the cope neck may behotter than the drag neck if pouring is interrupted to fill the riserwith metal from the pouring ladle. The temperature differential betweenroll body and roll necks usually increases with increasing ratiosbetween diameters of necks and bodies. It is to be understood that suchvariations and differentials in temperatures are within the scope of thepresent invention and are to be considered within the temperature rangesset forth herein. The present invention has been described inconjunction with rolls and it is to be understood that the terms "rolland rolls are intended to include the rough unfinished roll casting aswell as the finished roll.

The present invention is applicable broadly to all alloyed cast ironrolls which are sufliciently alloyed that in conventional or normalcooling after casting and solidification are characterized by amartensitic matrix structure at the face of the roll body and neck. Theinvention includes rolls having any combination of alloy elementsproducing unmachinable structures, such as martensitic and relatedproducts, on slow cooling, and capable of being isothermally transformedin a reasonable time to machinable austenite decomposition products. Asan illustrative example, alloyed cast irons which have been used in themanufacture of such martensitic rolls include those sold under thetrade-mark and falling within the range of about 2.75% to 3.75% carbon,about 0.25% to 1.75% silicon, about 0.15% to 1.65% manganese, about 3.5%to 6.5% nickel, and about 0.5% to 2.25% chromium. In tive amount up toabout 2.5% tungsten or vanadium, of boron,

of molybdenum, and/or up to about 0.15% or more, may also be present.Other While roll necks, etc., are

addition, a small but eifec- An illustrative example of a definite chilltype roll is one made of an alloy cast iron containing from about 3.2%to 3.5% carbon, about 0.5%

silicon, about 4.5% nickel, about 1% chromium, and about0.25%-manganese. This composition is widely employed and is normallyallowed to'cool in the mold. Another example of definite chill type rollis one made of an alloy cast iron containing about 3.2% carbon, about0.6% silicon, about 0.3% phosphorus, about 0.1% sulfur, about 0.25%manganese, about 4.75% nickel, 0.75% chromium, and about 0.4%vmolybdenum. -An illustrative example of an indefinite chill type orgrain type roll-is one made of an alloy cast iron containing about 3.2%carbon, about 1 to 1.5% silicon, about 4.5% nickel, about 2% chromium,and about 1.25 to 1.5% manganese. This composition normally is strippedfrom the mold while hot and cooled in afurnace. Another example of anindefinite chill type roll is one made of a high manganese type of alloycast iron containing about 3.4% carbon, about 0.9% silicon. about 0.2%phosphorus, about 0.06% sulfur. about 4.5% nickel, about 1.85% chromiumand about 1.4% manganese. An indefinite chill type roll made of a lowmanganese type'of alloyed cast iron has the same composition except thatthe manganese content is about 0.3%. By-raising the silicon content ofthe preceding high manganese composition and low manganese compositionto about 1.5% a grain type rollis obtained.

While the type of rolls having the composition sold under the trade-mark,of Ni-Hard comprises a substantial proportion of all the commercialalloy working rolls made, other alloy combinations are not excluded fromthe scope of this invention. In general, martensitic alloyed cast ironrolls will contain at least an effective amount of one or morestabilizing alloy elements. Thus, one or more of the following elements.nickel, manganese, molybdenum, vanadium, copper, chromium, tungsten,boron, tellurium, in amounts up to about ten percent total may be addedto a cast iron base composition of about 2 to 3.75% carbon,- about 0.3to 2% silicon, about 0.2 to 0.7%

manganese with the usual impurities and incidental or minor elements,including sulfur and phosphorus. to produce hard rolls. For example onecombination which has been-proposed for commercial application is carbonabout 3.2%, silicon about 0.5%, manganese about 0.4%, nickel about 2.5%,molybdenum about 2.5%, and chromium about 0.5% and another is carbonabout 3%, silicon about 0.6%, manganese'about- 4.5%, copper about 4%,and molybdenum about The invention includes any alloy combination whichproduces hard martensitic rolls which are susceptible to isothermaltreatment to improve the machinability of the necks.

The alloy cast iron rolls provided by the present invention are of thechill type and are characterizedby a roll body having a hard martensiticface or chill and, integral with the roll body, roll necks of the samecomposition as the face or body having a machinable structure contain-70 ing pearlite and/or allied subcritical transformation productswhereby said'necks may be satisiactorily machined in commercial practicewithout necessitating costly grinding operations except possibly forfinal surfacing and the like. It 75 is understood that in addition tomartensite in the roll body, carbides are always present, at least inthe face or chill, and in the so called grain rolls some graphite isalso intentionally present in the chilled face.

The present invention is particularly applicable to the production oflarge diameter rolls used in industry, including steel mill rolls, rollsfor rolling non-ferrous materials, crushing rolls,

paper mill rolls, and to other castings'made of m martensitic matrixirons which have extensions which must be made machinableand softened.

Although the present invention has been described in connection withpreferred embodiments, it isto be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as

those skilled in the art will readily understand.

Such variations and modifications are considered to be Within thepurview and scope of the appended claims.

We claim:

l. A method of producing alloyed cast iron rolls having a hardmartensitic body and machinable necks of the same composition as thebody which comprises pouring into a mold an al-' loyed cast iron rollhaving a body and necks which would be martensitic on being allowed tocool at a rate at least as slow as cooling in air, slowly coolingsaid-roll from solidification temperatures and while still hot from itsoriginal heat of castingv to temperatures above 500 F. and below thecritical temperature, holding said necks at said temperatures whilestill hotirom 3 their original heat of casting for more than one ofpearlite and hour to transform the structure of the necks to at leastone constituent from the group consisting intermediate transformationproducts while the slow cooling of said body is continued, slowlycooling the thus-treatednecks and transforming the matrix structure ofat least the face of the body below 500 F. to unmachinable martensitewhile said body is still hot from its original heat of casting.

2. A method of producing alloyed cast iron rolls having a hardmartensitic face and machinable necks of substantially the samecomposition as the body which comprises casting an alloyed cast ironroll having a body and necks which would be martensitic on being allowedto cool in the mold in which said roll is cast, slowly cooling said rollfrom solidification temperatures and while still hot from its originalheat of casting, interrupting the slow cooling of thenecks fromsolidification temperatures and while still hot" 1 from their originalheat of casting at temperatures below the temperature at which austeniteis stable but above 500 F., treating said necks while still hot fromtheir original heat of casting between said temperatures ,for more thanabout 10 hours while the slow cooling of said body metal containingabout 2% to 3.75% carbon,

0.3% to 2% silicon, a. small but effective amount j up to 10% of atleast one element from the group consisting of nickel, manganese,molybdenum,

, vanadium, copper, chromium. tungsten, boron and tellurium, and thebalance substantially all iron, slowly cooling said cast roll andarresting the slow cooling of the necks from solidification temperaturesand while still not from their original heat of casting at temperatureswithin the range of 500 F. to 1300 F., treating said necks still hotfrom their original heat of casting within said range for about 10 toabout 200 hours while the slow cooling of the body is continued, slowlycooling the thus-treated necks and transforming the matrix structure ofthe body below 500 F. to martensite while said body is still hot fromits original heat of casting, whereby an im= proved roll is obtainedhaving a hard body containing martensite and integral with said bodymachinable necks of the same composition.

4. A method of producing martensitic alloyed cast iron rolls havingmachinable necks of the same composition as the body which comprisescasting a cast iron roll having a body and necks which would bemartensitic on being allowed to cool to atmospheric temperatures in themold in which said roll is cast, slowly cooling said cast roll whilestill hot from its original heat of casting from solidificationtemperatures to temperatures within the range of 500 F. to 1300 F.,interrupting the slow cooling of the necks from solidificationtemperatures and while still hot from their original heat of castingwithin said range of temperatures, maintaining the necks of said rollwhile still hot from their original heat of casting within saidtemperature range while the'slow cooling of the body is continued totransform at least 50% of the structure of the neck to machinableaustenite decomposition products,

said transformed structure being substantially devoid of temperedmartensite,slowly cooling the thus-treated necks and transformingthematrix structure of the body below 500 F. to martensite while said bodyis stil1 hot from its original heat of casting, and thereaftersubjecting said roll to a stress relief treatment.

5. A method of producing martensitic alloyed cast iron rolls havingmachinable necks'ot the same composition as the body which comprisespouring a cast iron roll having a body and necks which would bemartensitic on being allowed to cool to atmospheric temperatures in themold in which said roll is cast, slowly cooling said roll fromsolidification temperatures and while still hot from its original heatof casting to temperatures within the range of 900 F. to 1100 F.,maintaining the necks of said roll within said temperature range whilestill not from their original heat of casting for about 10 to about 50hours while the slow cooling oi the bodyis continued, slowly cooling thethus-treated necks and transforming the matrix structure of at least theface of the body below 500 F. to unmachinable martensite while said bodyis still but from its original heat 01' casting, whereby an improvedmartensitic roll is obtained having machinable necks of the samecomposition as the body and integral therewith.

6. .A method of producing martensitic alloyed cast iron rolls havingmachinable necks of the same composition as the body which comprisespouring a roll having a body and necks from moltencast iron containingabout 2% to 3.75% carbon, 0.3% to 2% silicon, a small but eifectiveamount upto 10% of at least one element from the group consisting ofnickel, manganese, molybdenum, vanadium, copper, chromium, tungsten,boron and tellurium, and the balance substantially all iron, slowlycooling said roll while still aseavso hot from its original heat ofcasting from solidification temperatures to temperatures within therange of 900 F. to 1100 F., maintaining the necks oi. said roll stillhot from their original heat of casting within said temperature rangefor about 10 to about 50 hours while the slow cooling of the body iscontinued, slowly cooling the thus -treated necks and transforming thematrix structure of at least the face of the body below 500 F. tounmachinable martensite while said body is still hot from its originalheat of casting, and thereafter subjecting said roll to stress relievingtreatment within the range of 400 F. to 600 F., whereby an improvedmartensitic roll is obtained having machinable necks of the samecomposition as the body and integral therewith.

7. A method of producing alloyed cast iron rolls having a body with ahard unmachinable martensitic face and machinable necks of the samecomposition as the body of the roll from cast iron which would bemartensitic at least at the face-of said roll when allowed to cool inthe mold in which the roll is cast which comprises casting and slowlycooling the roll made of said cast iron, arresting the slow cooling ofthe necks from solidification temperatures while still hot from theiroriginal heat of casting a ove. 500 F. but below 1400 F. and holdingsaid necks be-' tween said temperatures to transform at least 50% of thematrix structure of the neck from austenite to atleast one constituentselected from the group consisting of pearlite and intermediatetransformation products while slowly cooling the body of the roll, andtransforming'the face of said slowly cooled body from austenite-tomartensite below 500 F. while said body is still hot from its originalheat of casting.

8. A method of producing alloyed cast iron I rolls having a body with ahard martensitic face and having machinable necks of the samecomposition as the body of the roll which comprises casting a roll fromcast iron' having a composition within the range of about 2% to 3.75%carbon, 0.3%v to 2% silicon, and a small but efiective amount up to 10%of at least one element from the group consisting of nickel, manganese,mo-

lybdenum, vanadium, copper, chromium, tungsten, boron, and tellurium,slowly cooling said roll while still hot from its original heat ofcasting from solidification temperatures to below 1400" F. but above 500F., maintaining said necks 01 said roll below 1400 F. but above 500 Flwhile still hot from their original heat ofjcasting for over one hour totransform at least 50% of the matrix structure of said necks fromaustenite to at least one constituent from the group consisting ofpearlite and intermediate transformation products formed above 500 F.while slowly cooling the body of the roll, and transforming at least theface of said slowly cooled body below 500 F. from austenite tomartensite while said body is still hot from its original heat ofcasting. V

9. A method of producing alloyed cast iron rolls having a body with ahard unmachinable martensitic face and machinable necks of the samecomposition as the body of the roll which comprises casting a roll fromcast iron containing about 2% to 3.75% carbon, 0.3% to 2% silicon, asmall but effective amount up to 10% from the group consisting ofnickel, manganese, molybdenum, vanadium, copper, chromium, tungsten,

. boron and tellurium, and the balance substantialcation temperaturesand while still hot from their original heat of casting at a temperaturebelow I the critical temperature but above 500 F., main- .lected fromthe group consisting of pearlite and intermediate transformationproducts while the slow cooling of the body is continued, slowly coolingthe thus-treated necks and transforming the matrix structure of at leastthe face of the slowly cooled body below 500 F. to unmachinable mar"-tensite while said body is still hot from its origthe said slowly cooledbody from austenite to martensite at temperatures below 500 F. whilesaid'body is still hot from its original heat of casting.

10. A method of producing an alloyed cast iron roll having a body with'a hard martensitic face andmachinable necks of the same composition asthe body of the roll which comprises pouring into a mold an integralroll made of alloyed cast iron which would have a martensitic structureat the face'of the roll on being allowed to cool at a rate at least asslow as cooling in air and then conducting the slow cooling of the necksand the slow cooling of the body from solidification temperatures in amanner to transform the structure of the roll necks, while still hotfrom their original heat 'of casting,'between 1400 F. and 500 F. fromaustenite to a machinable matrix product and to transform thestructureof the face of the roll body,'while still hot from its originalheat of casting, 7 below 500 F. from austenite to a martensiticunmachinable product.

11. A method of producing an alloyed cast iron roll having a body with ahard, unmachinable martensitic face and machinable necks ofthe samecomposition as the body of theroll which neck-like extension of lesserdiameter and of the inal heat of casting. v

13. A method of producing an alloyedcast iron casting having a body witha hard martensitic face and integral with said body a'machinable samecomposition as the body which comprises pouring said casting'from moltencast iron havtension while still but from its original heat of castingat elevated temperatures below 1400 F. but above 500 F. for over onehour and up to 200 hours to at least partially transform said necklikeextension from austenite to at least one machinable' decompositionproduct of austeniteselected-from the group consisting of pearlite. and

I intermediate transformation products while the comprises pouring andslowly cooling an integral 7 alloyed cast iron roll, arresting the slowcooling of the necks from solidification temperatures above '500? F. butbelow 1300 F. while the necks are still hot from their original heat ofcasting, holding said necks between said temperatures while still hotfrom their original heat of casting tegral with the body of the rollwhich comprises slowly cooling said martensitic alloyed cast iron rollfrom solidification temperatures and while still hot from its originalheat of casting, arresting the slow cooling of the necks while still hotfrom their original heat-of casting at temperatures within the range of1300 F. to 500 F., maintaining said necksv for more than one hour withinsaid range of temperatures while still hot from their original heat ofcasting to transform at least of the austenitic structure of the necksto austenite decomposition products se body of the casting continues tocool slowly, and transforming the matrix structure of at least the faceof said slowly cooled body below 500 F. from austenite to a hardmartensitic product while said body is still hot from its original heatof casting.

' 14. A method of producing an alloyed cast iron 1 element from thegroup consisting of nickel, manganese, molybdenum, vanadium, copper,chromium, tungsten, boron and tellurium, slowly cooling said cast roll,arresting the slow cooling of the necks from solidification temperatureswhile still hot from their original heat of casting at, elevatedtemperatures below the critical temperature but above 500 F. to at leastpartially transform said necks from austenite to at least one'machinable decomposition product of austenite selected from the groupconsisting of pearlite and intermediate transformation products whilethe body of the roll slowly cools, and transforming at least the face ofsaid slowly cooled body below 500 F. from austenite to a hardmartensitic prod-

